This invention relates to treatment of migraine syndrome.
A working definition of migraine is a benign recurring headache and/or neurologic dysfunction, more common in women than men.
Classic migraine (migraine with aura) refers to the syndrome of a severe, throbbing headache which often is preceeded by sensory, motor or visual symptoms, referred to as an xe2x80x9caura.xe2x80x9d Common migraine (migraine without aura) denotes a headache without the aura. Common migraine is the most frequent headache type reported by patients.
Many drugs are now available for prophylactic treatment of migraine. They must be taken daily. The major drugs for prophylaxis are propanolol, amitriptyline, valproate, verapamil, phenelzine, and methysergide. Use of methysergide carries with it the danger of retroperitoneal fibrosis. Aspirin-like drugs, including aspirin, naproxen, ibuprofen, mefenamic acid, flufenamic acid, and tolfenamic acid are in use as prophylactic agents. The high dosage of these compounds required for effectiveness is a drawback. It has been estimated that the probability of success with any one of the available prophylactic antimigraine drugs is about 60 to 75% (Harrison""s Principles of Internal Medicine, eds. Isselbacher et al., McGraw-Hill, Inc., New York, 1994, p. 69). Accordingly, development or identification of drugs for prophylactic treatment of migraine is an area of continuing medical need.
The invention features administering sulfamates of the following formula (I): 
wherein X is O or CH2 and R1, R2, R3, R4, and R5 are as hereinafter defined, to prophylactically control migraines in non-epileptic subjects. The most preferred compound is topiramate, described below. Topiramate has been used to treat epileptics, including epileptics who suffer from migraine, to prevent seizures.
The above discussed and other features and attendant advantages of the present invention will become better understood by reference to the following detailed description of the invention, and from the claims.
By treating migraine patients with the sulfamate compound of formula (I) or a pharmaceutically acceptable salt or derivative thereof, a substantial decrease in frequency of migrainous episodes can be achieved.
The administered compound is a sulfamate of the following formula: 
wherein
X is CH2 or oxygen;
R1 is hydrogen or lower (C1-C6) alkyl; and
R2, R3, R4 and R5 are independently hydrogen or lower alkyl and, when X is CH2, R4 and R5 may be alkene groups joined to form a benzene ring and, when X is oxygen, R2 and R3 and/or R4 and R5 together may be a methylenedioxy group of the following formula (II): 
xe2x80x83wherein
R6 and R7 are the same or different and are hydrogen, lower alkyl or are alkyl and are joined to form a cyclopentyl or cyclohexyl ring,
R1 in particular is hydrogen or alkyl of about 1 to 4 carbons, such as methyl, ethyl and iso-propyl. Alkyl throughout this specification includes straight and branched chain alkyl. Alkyl groups for R2, R3, R4, R5, R6, and R7 are preferably of about 1 to 3 carbons and include methyl, ethyl, iso-propyl and n-propyl. When X is CH2, R4 and R5 may combine to form a benzene ring fused to the 6-membered X-containing ring, i.e., R4 and R5 are defined by the alkatrienyl group xe2x95x90CHxe2x80x94CHxe2x95x90CHxe2x80x94CHxe2x95x90.
In a particular group of compounds of formula (I), X is oxygen and both R2 and R3 and R4 and R5 together are methylenedioxy groups of the formula (II) wherein R6 and R7 are both hydrogen, both alkyl or combine to form a Spiro cyclopentyl or cyclohexyl ring, in particular where R6 and R7 are both alkyl such as methyl. A second group of compounds is that wherein X is CH2 and R4 and R5 are joined to form a benzene ring. A third group of compounds of formula (I) is that wherein both R2 and R3 are hydrogen.
Compounds of formula I which are preferred for use in the method of the invention are tetrahydro-2H-pyran-2-yl)methane sulfamate, 2,3:4,5-bis-O-(1-methylethyldiene)-xcex2-D-fructopyranose sulfamate, and 2,3:4,5-bis-O-(1-methylethyldiene)-xcex2-D-fructopyranose methylsulfamate. A most preferred compound is 2,3:4,5-bis-O-(1-methylethyldiene)-xcex2-D-fructopyranose sulfamate, also known as topiramate, having the chemical structure shown in formula III: 
By pharmaceutically acceptable derivative is meant any pharmaceutically acceptable ester or salt of such ester of the compounds of formula (I) or any other compounds which upon administration to the recipient is capable of providing (directly or indirectly) a compound of formula (I) or an anti-migraine active metabolite or residue thereof.
It will be appreciated by those skilled in the art that the compounds of formula (I) may be modified to provide pharmaceutically acceptable derivatives thereof at any of the functional groups in the compounds. Of particular interest are derivatives in which the sulfamate portion is masked by an imidate group that can be removed in a physiological milieu to generate the parent drug, as disclosed in U.S. Pat. No. 5,258,402, and incorporated herein by reference. Such derivatives are commonly known as prodrugs. Other derivatives of interest include sorbopyranose sulfamates (U.S. Pat. No. 5,384,327), fructopyranose cyclic sulfites and sulfates (U.S. Pat. No. 5,242,942), and phenylethyl sulfamates (U.S. Pat. No. 4,792,569), as well as acetazolamide U.S. Pat. Nos. 2,554,816 and 2,980,679).
It will be appreciated by those skilled in the art that the pharmaceutically acceptable derivatives of the compounds of formula (I) may be derivatised at more than one position.
Pharmaceutically acceptable salts of the compounds of formula (I) include those derived from pharmaceutically acceptable, inorganic and organic acids and bases. Examples of suitable acids include hydrochloric, hydrobromic, sulphuric, nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic, salicylic, succinic, toluene-p-sulphonic, tartaric, acetic, citric, formic, benzoic, malonic, napthalene-2-sulphonic and benzenesulphonic acids. Other acids such as oxalic acid, while not in themselves pharmaceutically acceptable, may be useful in the preparation of salts useful as intermediates in obtaining compounds useful in the method of the invention and their pharmaceutically acceptable acid addition salts.
Salts derived from appropriate bases include alkali metal (e.g. sodium), alkaline earth metal (e.g. magnesium) ammonium and NR4 (where R is C1-4 alkyl) salts.
Synthesis. The anti-migraine sulfamate derivatives employed in the method of the invention can be synthesized according to the methods disclosed in U.S. Pat. No. 4,513,006, which is incorporated by reference. Other methods well known in the art for preparing the disclosed sulfamate compounds, precursors, prodrugs, or derivatives thereof are,also available, for example, those disclosed in U.S. Pat. Nos. No. 5,258,402, 5,384,327, 5,242,942, 4,792,569, 2,554,816 and 2,980,679, all of which are incorporated by reference.
Pharmaceutical Compositions. Pharmaceutical compositions of the anti-migraine sulfamate derivatives of the invention can be prepared according to the methods disclosed in U.S. Pat. No. 4,513,006, which is incorporated by reference.
Treatment and Dosage. The amount of a compound of formula (I) useful for treatment of migraine in non-epileptic subjects will vary not only with the particular compound selected but also with the route of administration, and the age and condition of the patient treated. In general, suitable doses are in the range of from about xc2xd to 15 mg/kg body weight per day, preferably in the range of 1 to 10 mg/kg day, most preferably in the range of 1 to 5 mg/kg day. The method of the invention can conveniently administer daily dosages of compounds of formula (I) in unit dosages, for example, containing 50 to 400 mg, conveniently 100 to 200 mg, of active ingredient per unit dosage form. Suitable treatment is given 1 or 2 times daily, depending upon clearance rate. Accordingly, the desired dose may be presented in a single dose or as divided doses administered at appropriate intervals, for example as two, three, four or more sub-doses per day.
Treatment is preferably commenced before the onset of a migraine episode and continued indefinitely.
While it is possible that, for use in the method of the invention, compounds of formula (I) may be administered as the raw chemical, it is preferable to present the active ingredient as a pharmaceutical formulation or composition which may further include a pharmaceutically acceptable carrier. The carrier must be xe2x80x98acceptablexe2x80x99 in the sense of being compatible with the other ingredients of the formulation and not deleterious to patient.